Anenomefish Make Extremely Dutiful Dads

Brilliance | Dec. 15, 2017

When Disney created a film about a clownfish father searching for his missing son (Finding Nemo), who knew that their storyline was backed by science? You see, clownfish, or anemonefish, fathers have razor-sharp paternal instincts. Thanks to a May 2017 study by researchers at the University of Illinois at Urbana-Champaign, we now know why.

Anenomefish Dads Aren't Clowning Around

Imagine the biggest helicopter parent you know, multiply their antics by 100, and you have anemonefish dads. According to the study's press release, "if you give a bachelor anemonefish a scoop of anemonefish eggs from an unrelated nest, he will care for them—constantly nipping at them to remove debris and fanning them with oxygen-rich waters—as if they were his own." Now that's fatherly love. But why put in so much effort for eggs that aren't your own? Their study points to a potent hormonal signal called isotocin, which is similar to oxytocin, the "love" hormone in humans. As soon as the researchers blocked isotocin in the male fish, the dads began ignoring their offspring.

Anemonefish carry another hormone evolving from the same gene: arginine vasotocin. This hormone typically regulates dominance and aggression, but when the researchers blocked arginine vasotocin in the anemonefish dads, something unusual happened: they "became even more attentive to their offspring." How can that be? Ross DeAngelis, a graduate assistant who c0-led the study, explains their hypothesis: "by blocking vasotocin signaling, you're reducing vigilance and nest defense, allowing a greater allotted effort to be directed toward parental care." Without the urge to fight off predators, you have more energy to spend doting on the kiddos.

Dad Genes

What could this mean for paternal instincts in humans? The researchers honestly aren't sure. Paternal instincts are notably rare in vertebrates (especially mammals), but it's worth mentioning that oxytocin does play a role in human fathering. In fact, studies find that fathers interacting with their baby experience an increase in that cuddly hormone. The researchers also suspect that the genetics of paternal care spread across species. Beyond that—more research needs to be done.